What would happen to Earth's climate if all the carbon that's currently sequestered as fossil fuels were to be dug up and burned? In light of human efforts to continuously ignore signs that such a thing might be a bad idea, Hansen et al. present their model's findings on how much global warming human activity could cause.

Burning all fossil fuels would produce a different, practically uninhabitable, planet. Let us first consider a 12 W m−2 greenhouse forcing, which we simulated with 8×CO2. If non-CO2 GHGs such as N2O and CH4 increase with global warming at the same rate as in the palaeoclimate record and atmospheric chemistry simulations [122], these other gases provide approximately 25% of the greenhouse forcing. The remaining 9 W m−2 forcing requires approximately 4.8×CO2, corresponding to fossil fuel emissions as much as approximately 10,000 Gt C for a conservative assumption of a CO2 airborne fraction averaging one-third over the 1000 years following a peak emission [21,129].

Our calculated global warming in this case is 16°C, with warming at the poles approximately 30°C. Calculated warming over land areas averages approximately 20°C. Such temperatures would eliminate grain production in almost all agricultural regions in the world [130]. Increased stratospheric water vapour would diminish the stratospheric ozone layer [131].

It sounds pretty difficult to do but I think if we all put our minds to it we could make it happen.